Actuators 2013, 2(3), 59-73; doi:10.3390/act2030059

Concept of a Series-Parallel Elastic Actuator for a Powered Transtibial Prosthesis

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Received: 21 February 2013; in revised form: 24 June 2013 / Accepted: 25 June 2013 / Published: 3 July 2013
(This article belongs to the Special Issue Human Centered Actuators)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: The majority of the commercial transtibial prostheses are purely passive devices. They store energy in an elastic element during the beginning of a step and release it at the end. A 75 kg human, however, produces on average 26 J of energy during one stride at the ankle joint when walking at normal cadence and stores/releases 9 J of energy, contributing to energy efficient locomotion. According to Winter, a subject produces on average of 250W peak power at a maximum joint torque of 125 Nm. As a result, powering a prosthesis with traditional servomotors leads to excessive motors and gearboxes at the outer extremities of the legs. Therefore, research prototypes use series elastic actuation (SEA) concepts to reduce the power requirements of the motor. In the paper, it will be shown that SEAs are able to reduce the power of the electric motor, but not the torque. To further decrease the motor size, a novel human-centered actuator concept is developed, which is inspired by the variable recruitment of muscle fibers of a human muscle. We call this concept series-parallel elastic actuation (SPEA), and the actuator consists of multiple parallel springs, each connected to an intermittent mechanism with internal locking and a single motor. As a result, the motor torque requirements can be lowered and the efficiency drastically increased. In the paper, the novel actuation concept is explained, and a comparative study between a stiff motor, an SEA and an SPEA, which all aim at mimicking human ankle behavior, is performed.
Keywords: series-parallel elastic actuation; compliant actuation; high torque requirements; energy efficiency
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MDPI and ACS Style

Mathijssen, G.; Cherelle, P.; Lefeber, D.; Vanderborght, B. Concept of a Series-Parallel Elastic Actuator for a Powered Transtibial Prosthesis. Actuators 2013, 2, 59-73.

AMA Style

Mathijssen G, Cherelle P, Lefeber D, Vanderborght B. Concept of a Series-Parallel Elastic Actuator for a Powered Transtibial Prosthesis. Actuators. 2013; 2(3):59-73.

Chicago/Turabian Style

Mathijssen, Glenn; Cherelle, Pierre; Lefeber, Dirk; Vanderborght, Bram. 2013. "Concept of a Series-Parallel Elastic Actuator for a Powered Transtibial Prosthesis." Actuators 2, no. 3: 59-73.

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